Weed Management in Corn 1

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1 SS-AGR-02 Weed Management in Corn 1 J.A. Ferrell, G.E. MacDonald, and R. Leon 2 Successful weed control is essential for economical corn production in Florida. Weeds reduce corn yields by competing for moisture, nutrients, and light during the growing season and interfere with harvest. Producing a good crop of corn is only half the battle and will not be profitable unless the corn can be harvested. Late-season weeds can result in excessive yield losses, inefficient equipment operation, and provide a source of weed seed for the following season. Weeds can be controlled in corn; however, this involves good management practices in all phases of corn production. Crop Rotations Crop rotations are beneficial not only in reducing weed problems in corn, but also in crops following in the rotation. Other benefits include reducing insects, diseases, and nematodes in corn and in succeeding crops. Crop Competition Crop competition is one of the most important but often overlooked tools in weed control. A good stand of corn, which emerges rapidly and uniformly and shades the middles early, is very important in reducing weed competition. This involves utilizing good management practices, such as choosing a well adapted hybrid, good fertility, maintaining proper soil ph, and using adequate plant populations. Utilizing these good management practices is necessary for controlling weeds and producing high yielding corn. The plant that emerges and grows most rapidly is usually the plant that will have the competitive advantage; therefore, everything possible should be done to ensure that the corn and not the weeds has this competitive advantage. Know Your Weeds Know your weeds and choose a herbicide that is effective for your specific weed problems. Generally, for preplant and preemergence applications, the weed problem must be anticipated since the weeds have not emerged at the time of application. This can best be done by observing the field in the fall and recording those weeds which are present and in what areas of the field they occur. These weed maps can be very useful the next spring in refreshing your memory and making decisions on which herbicides to purchase. Once your weed problems have been determined, Tables 4 and 5 can be helpful in determining the herbicide(s) that is most effective. Cultivation Cultivation is still a good and economical means of weed control. Few benefits other than weed control have been attributed to cultivation, and, in fact, there are disadvantages 1. This document is SS-AGR-02, one of a series of the Agronomy Department, Florida Cooperative Extension Service, Institute of Food and Agricultural Sciences, University of Florida. Revised November Revised November Please visit the EDIS website at 2. J.A. Ferrell, associate professor, Agronomy Department; G.E. MacDonald, professor, Agronomy Department; and R. Leon, assisant professor, West Florida Research and Education Center, Milton, FL; Florida Cooperative Extension Service, Institute of Food and Agricultural Sciences, University of Florida, Gainesville, FL The use of trade names in this publication is solely for the purpose of providing specific information. UF/IFAS does not guarantee or warranty the products named, and references to them in this publication do not signify our approval to the exclusion of other products of suitable composition. Use herbicides safely. Read and follow directions on the manufacturer s label. The Institute of Food and Agricultural Sciences (IFAS) is an Equal Opportunity Institution authorized to provide research, educational information and other services only to individuals and institutions that function with non-discrimination with respect to race, creed, color, religion, age, disability, sex, sexual orientation, marital status, national origin, political opinions or affiliations. U.S. Department of Agriculture, Cooperative Extension Service, University of Florida, IFAS, Florida A&M University Cooperative Extension Program, and Boards of County Commissioners Cooperating. Nick T. Place, Dean

2 to cultivation. Cultivation can disrupt the roots of corn, increase moisture loss from the soil, and bring more weed seed to the surface to germinate. Therefore, if good weed control has been achieved with herbicides, then the need to cultivate is questionable. report for preemergence or post-emergence application can be used in no-till corn just as in conventional corn. Herbicides Herbicides are one of the most effective tools for successful weed control in corn. Preplant or preemergence applications combined with the previously-discussed management practices are important for ensuring that the corn has the initial competitive advantage. If the corn is taller than the weeds, then postemergence directed applications can be utilized to extend the weed control through the season. If the weeds are as tall as the corn, then this option is not available. Late-season, over-the-top applications can be used to aid in harvest efficiency, although in most cases this will not be needed if good weed control was achieved throughout the season and the corn is harvested when mature. The herbicides suggested in Table 1, Table 2, and Table 3 are those that have performed well in IFAS research. When choosing a herbicide, consideration should be given to the crop which will follow in a rotation and whether the herbicide will carry over and injure the succeeding crop. Read the label and follow all instructions and precautions. Accurate sprayer calibration is extremely important since rates too low may not provide adequate weed control and rates too high may injure the crop or result in carry over and injury to succeeding crops. Herbicides, like any pesticide, should be handled with care. Store herbicides behind locked doors in the original containers with the label intact and separated from seed, fertilizers, and other pesticides. Weed Control in No-Till Corn Production practices in no-till corn virtually eliminate effective cultivation, thus placing greater importance on effective chemical weed control. Chemical weed control in no-till corn is similar to that in conventional planted corn with two basic differences: 1) Existing vegetative growth must be killed or suppressed with a herbicide at or before planting. These can be found under the Burndown Herbicides for No-Till Corn section (Table 1). 2) Herbicides requiring mechanical soil incorporation cannot be effectively used. All other herbicides listed in this 2

3 Table 1. Burndown Herbicides for No-Till Corn. Trade Name and Broadcast Rate/Acre of Commercial Product Gramoxone Inteon 1-2 qt Sharpen 2 oz/a Verdict or Integrity oz/a Several 1-2 qt burndown of ryegrass Common Name and Broadcast Rate/Acre of Active Ingredient paraquat saflufenacil saflufenacil + dimethenamid glyphosate Remarks Higher rate should be used for woody plants or sod if they are present. A proper surfactant must be added. Apply in gallons of solution per acre. Some regrowth from rye, oats, or wheat may occur after treatment. This may vary with small grain species, variety, and stage of growth. For these reasons, it is suggested that an application should be made days prior to planting. If regrowth occurs, retreat at planting or prior to emergence of the corn. Good coverage is essential for effective control. Including 2,4-D at 1 qt/a will improve control of wild radish and cutleaf eveningprimrose. For burndown and short-lived residual of many broadleaf weed species. Sharpen will not control large wild radish or cutleaf eveningprimrose. A methylated seed oil adjuvant is essential for maximum effectiveness. Do not apply more than 6 oz/a/yr. Treated corn can be harvested for silage after 80 days. Similar to Sharpen, but improved preemergence grass control due to the presence of dimethenamid. Do not apply more than 25 oz/a/yr. Can be harvested for silage 80 days after application. Lower rate should be used on annual weeds and higher rate on perennial weeds. Apply in gallons of water. See label for additional information. For control of most annual weeds. Rate of kill may be slow during cool weather. Will not supply residual control and should be used in conjunction with a residual herbicide as previously discussed. Choose the residual herbicide or combination of herbicides based on anticipated weeds. Tank-mixes with certain residual herbicides such as atrazine may result in some reduction of activity. Consult label for appropriate tank mixes. Including 2,4-D at 1 qt/a will improve control of wild radish and cutleaf eveningprimrose. For information on control of ryegrass prior to corn planting, see the publication SS-AGR-269 Burndown of Ryegrass Cover Crops prior to Crop Planting, 3

4 Table 2. Weed Management in Corn. Trade Name and Broadcast Rate/Acre of Commercial Product Atrazine 1 or AAtrex (several formulations) AAtrex or Atrazine 1 (several formulations) 80W 90DG 4L Simazine 4L (several trade names)1-2 qt Outlook, Slider, or Sortie oz Axiom oz/a Dual II Magnum or Dual Magnum pt or Stalwart, Parallel pt Aim 2 EC oz/a Common Name and Broadcast Rate/Acre of Active Ingredient atrazine (1-2 lb) atrazine ( lb) simazine PREPLANT PREEMERGENCE S-dimethenamid flufenacet + metribuzin S-metolachlor or metolachlor POSTEMERGENCE carfentrazone Remarks Controls most broadleaf weeds and some grasses. Tank mix with a grass herbicide for broader spectrum control. Do not use more than 2.5 lbs ai/a/year. Good broadleaf weed control but less effective on grasses. Use the lower rate on light sandy soils. Under dry conditions a shallow cultivation may improve control. Do not graze or feed treated forage to livestock for 21 days after application. Do not use more than 2.5 lbs ai/a/year. Refer to herbicide table and label for specific product. Similar to atrazine but requires more rainfall for activation and is generally less effective in control of certain broadleaf weeds. Good control of crabgrass and fall panicum. Similar in control to metolachlor. Application rate is dependant on soil texture and organic matter percentage - see product label for specific details. May be harvested for silage 40 days or more after application. Many premix products available that also contain atrazine. Provides annual grass and small-seeded broadleaf control similar to metolachlor. Specific use rate dependent upon soil texture and organic matter. Corn should be planted deep. Can be tank-mixed with atrazine for improved control of broadleaf weeds. Corn and soybeans can be planted any time after an application of Axiom. A 12-month rotation restriction exists for the following crops: rye, sorghum, wheat, cotton, peanuts, and tobacco. Controls most annual grasses (except Texas panicum) and certain broadleaf weeds. Fair to good control of yellow nutsedge. Under cool, wet weather conditions, stunting or crop injury expressed as malformed, knotted, twisted top growth may occur. Corn normally outgrows early season injury. Metolachlor may be tank-mixed with atrazine or simazine. Metolachlor can be applied up to 40 tall corn. Available in several premixes with atrazine (Bicep II Magnum, Cinch ATZ, Stalwart Xtra, and others). The metolachlor formulations (Parallel, Stalwart, others), in contrast to S-metolachlor, have not provided the same length of residual control of certain weeds as similar rates of Dual Magnum formulations in some field trials. For the control of pigweed, annual morningglory species (except smallflower), and tropical spiderwort. Can be applied over the top of corn until the V8 stage of growth. Aim will cause crop injury in the form of leaf speckling and necrosis but this injury will not affect yield. Use in combination with a crop oil 1% v/v (1 gal/100 gals). Aim can be tank-mixed with glyphosate (GR corn hybrids only), 2,4-D, atrazine, and Accent. 4

5 Accent 75DF, Primero, others 2/3 oz/a Accent Q 54.5 WDG 0.9 oz/a Nic-it 2 SC 2 fl. oz/a Atrazine or AAtrex qt Banvel, Clarity, Vision pt Basagran qt Buctril 2EC pt Callisto 3.0 oz 2,4-D amine pt/a nicosulfuron nicosulfuron + crop safener nicosulfuron atrazine dicamba bentazon bromoxynil mesotrione 2,4-D Single Application Controls many annual and perennial grasses, including johnsongrass. DO NOT apply to corn treated with Counter insecticide due to severe crop injury or mortality. Can be applied over-the-top of corn up to 20 inches tall or before the V6 stage (whichever is more restrictive) and post-directed up to 36 inches tall. A nonionic surfactant (0.25% v/v) or crop oil concentrate (1% v/v) is required. Refer to manufacturer s label for additive rates. Do not apply within 7 days to corn treated with foliar applied organophosphate insecticides or with herbicides containing bentazon or 2,4-D. DO NOT apply organophosphate insecticides within 3 days after applying Accent. Refer to manufacturer s label for sprayer cleanup. DO NOT apply within 30 days of harvest. Split Application For hard-to-control weeds, two applications of 0.67 oz/a can be applied 14 to 28 days apart. Follow all precautions listed for single application. DO NOT exceed 1.3 ozs/a/yr. Addition of a crop oil at the rate of 1 qt/a provides quicker kill of weeds. Apply before weeds exceed 2 in height and corn exceeds 12 in height. Most effective on broadleaf weeds. Do not apply with fluid fertilizer. Do not exceed 2.5 lb ai/a/yr. Good control of broadleaf weeds. Can be applied broadcast over the top at 1 pt from corn emergence to V5 or 8. From 8 to 36 tall corn, apply only 0.5 pt. Do not apply within 15 days before tassel emergence. Do not graze or harvest for dairy or beef feed prior to milk stage. Avoid spray drift to nearby sensitive crops. The addition of a surfactant is optional - do not use crop oils. Controls certain broadleaf weeds and yellow nutsedge. To control yellow nutsedge, 2 applications 7 to 10 days apart is generally required. Rate depends on weed species and size; therefore, refer to the label. Do not apply to corn that has been subjected to stress. Do not mix with other pesticides or fertilizers. Add crop oil at 1 qt/a. Controls cocklebur, bristly starbur and certain other broadleaf weeds when less than 3 in. tall. Adjust rate according to weed size and species as noted on label. Applications of Buctril often result in leaf burning on corn. This injury generally lasts 7 days and does not affect yield. Applications may be made up to 30 or 8-lf stage and should contain crop oil concentrate with 28% nitrogen or ammonium sulfate. Callisto can be applied sequentially, >14 days apart, if needed. Do not exceed 6.0 fl oz/a/ yr if applied postemergence, or 7.4 fl oz/a/yr if applied preemergence and postemergence. Do not apply in combination with organophosphate insecticides. Some bleaching may occur after application, but is temporary. May be applied to corn that is 5 to 8 in height - must be applied as a directed spray after corn is 8 or slight to moderate injury will result. If a herbicide with this mode of action is desirable but corn injury is a concern, Status herbicide would be a better choice. No adjuvant is needed. 5

6 Status 5-10 oz Dual II Magnum, Dual Magnum 1.0 pt Laudis 3 fl. oz/a Prowl pt or Prowl H pt + AAtrex or Atrazine 1 (several formulations) Sandea oz Prowl pt or Prowl H pt Resource fl oz Resolve Q 1.25 oz/a Steadfast Q 1.5 oz/a dicamba + diflufenzopyr + isoxadifen S-metolachlor tembotrione pendimethalin + atrazine halosulfuron pendimethalin flumiclorac rimsulfuron + thifensulfuron + crop safener nicosulfuron + rimsulfuron + crop safener For control of broadleaf weeds. Can be applied to 4 to 36 tall corn. Corn is more tolerant to Status than other dicamba or 2,4-D containing products. Best if applied with nonionic surfactant (0.25% v/v). Can be mixed with glyphosate or Liberty 280 (at 5 oz/a) if tolerant hybrids have been planted. Avoid drift to sensitive crops. Dual + atrazine should be applied before weeds are past 2-leaf stage and before corn is 5 tall. Applications of Dual Magnum may result in temporary leaf burning on corn. Dual will not control emerged weeds. Laudis provides excellent postemergence control (with soil residual activity) of several grass and broadleaf weeds. Tank mixes with glyphosate improve control of pigweeds, ragweed, and morningglory. Laudis can be applied from corn emergence to V8 growth stage. A maximum of 6 oz/a can be applied annually. Laudis should be applied with a crop oil or methylated seed oil adjuvant. Small grains can be planted within 4 months of application. Prowl + atrazine should be applied before the corn is in the 4-leaf stage and before weeds emerge. Prowl 3.3 requires irrigation or rainfall within 7 days to activate. Prowl H 2 0 is more tolerant to dry conditions after application. Controls yellow and purple nutsedge. Can be applied over-the-top from spike stage through layby stage. Use higher rates for nutsedge and larger weeds. The use of a non-ionic surfactant or crop oil is recommended. May be applied in a split application but do not exceed 2.67 oz/a/ year. Apply postplant and incorporate for late season control of annual grasses and certain small seeded broadleaf weeds. Apply after corn is 4 tall but before the last cultivation. Do not apply if Prowl was used as a preemergence application. Existing weeds must be killed before application. Incorporate with either: (1) sweeps or rolling cultivator or (2) rainfall or irrigation as soon as possible after application. Mix with Roundup for increased broadleaf control in transgenic Roundup Ready corn. Tall ivyleaf and entire leaf morningglory control is enhanced by adding Resource to glyphosate. Do not apply before the 2-leaf or after 10-leaf stage of corn development. Apply postemergence to corn that is up to 20 tall for the control of many annual grasses and broadleaf weeds. Will also provide some residual control. Do not apply to corn taller than 20 or exhibiting 7 or more leaf collars. Use in combination with a 0.25% v/v or 1% v/v + ammonium nitrogen fertilizer (2 qt/a UAN or 2 lb/a AMS). Can be tank-mixed with atrazine, glyphosate (RR corn) or Liberty (LL corn). Do not apply Resolve Q to corn that has been previously treated with an OP insecticide such as Counter, Lorsban, or Thimet. Similar to Resolve Q. 6

7 Treflan HFP or Triflualin 4EC ( pt) or Treflan TR-10 or Triflualin 10G ( lb) Evik DF lb Gramoxone Inteon pt Lorox DF lb 2,4-D amine 2 1 pt trifluralin ametryn paraquat linuron 2,4-D POST-DIRECTED Apply postplant and incorporate for late season control of annual grasses and certain small seeded broadleaf weeds. Apply after corn is a minimum of 8 tall as an over-the-top or as a directed spray. Must be incorporated by water or cultivation. If incorporated by water, a minimum of 0.5 to 1 inches will be necessary. Cultivate before application to kill existing weeds and throw soil to cover the base of corn plants. Incorporate with sweeps or rolling cultivator. Do not apply preplant or preemergence. Treflan TR-10 should be incorporated by cultivation. Use lb of TR- 10 to control fall or Texas panicum. Good control of grasses and broadleaf weeds. Most effective if weeds are less than 6 tall. Apply as directed spray after the smallest corn is at least 12 tall. Do not spray over top of corn. Use a surfactant at the rate recommended on the label. Do not graze or feed forage to livestock for 30 days after application. Can tank-mix with 2,4-D for improved broadleaf weed control. For control of emerged annual grass and broadleaf weeds. Apply as directed, spray after corn is 10 tall. Do not allow spray to contact more than the lower 3 of corn plants. Add 1 qt of a nonionic surfactant for 100 gal of spray. Do not mix with liquid fertilizer. Can be tankmixed with several herbicides. See label. Controls most grasses and broadleaf weeds up to 5 tall. Apply as a directed spray after corn is 15 tall. Use lower rate for 2 weeds and higher rate for 5 weeds. Do not spray over the top of corn. Use a surfactant at the rate recommended on the label. Can tank-mix with 2,4-D for improved broadleaf weed control. Controls broadleaf weeds, cocklebur, pigweed, ragweed, morningglory, and sicklepod (coffeeweed). Broadcast over the top when corn is spiking to 8 tall and weeds are small. Apply as directed spray to the base of the corn plant to minimize injury, after corn reaches 8 in height. Do not apply when corn is silking or tasseling. Avoid spray drift to nearby sensitive crops. 1 RESTRICTED USE PESTICIDE. WARNING: THE FOLLOWING STATEMENT HAS BEEN ADDED TO THE ATRAZINE LABEL. THIS STATEMENT SHOULD BE HEEDED BY ALL PROSPECTIVE USERS AND STEPS SHOULD BE TAKEN TO COMPLY WITH THIS LABEL CHANGE. ATRAZINE IS A CHEMICAL WHICH CAN TRAVEL (SEEP OR LEACH) THROUGH SOIL AND CAN CONTAMINATE GROUND WATER AS A RESULT OF AGRICULTURAL USE. ATRAZINE HAS BEEN FOUND IN GROUND WATER AS A RESULT OF AGRICULTURAL USE. USERS ARE ADVISED NOT TO APPLY ATRAZINE WHERE THE WATER TABLE (GROUND WATER) IS CLOSE TO THE SURFACE AND WHERE THE SOILS ARE VERY PERMEABLE, I.E., WELL-DRAINED SOILS SUCH AS LOAMY SANDS. YOUR LOCAL AGRICULTURAL AGENCIES CAN PROVIDE FURTHER INFORMATION ON THE TYPE OF SOIL IN YOUR AREA AND THE LOCATION OF GROUND WATER. IN ADDITION, SOME PRODUCT LABEL STATEMENTS INCLUDE AS A FURTHER QUALIFICATION OF RISKY SOILS, SOILS CONTAINING SINKHOLES, OVER LIMESTONE BEDROCK, SEVERELY FRACTURED SURFACES, AND SUBSTRATES WHICH WOULD ALLOW DIRECT INTRODUCTION INTO AN AQUIFER. 2 See fact sheet SS-AGR-12 Florida s Organo-Auxin Herbicide Rule for state rules pertaining to application of organo-auxin herbicides in Florida. NOTE: Herbicide recommendations in this report are contingent upon their registration by the EPA. If a registration is canceled, the herbicide would no longer be recommended. 7

8 Table 3. Postemergence Herbicide Tolerant Varieties. Trade Name and Broadcast Rate/Acre of Commercial Product Liberty oz/a Sequence pt/a Expert qt/a Halex GT pt/a Roundup WeatherMax fl oz (44 fl oz/a/yr) glyphosate (4 lb) 32 fl oz (64 fl oz/a/yr) glyphosate (5 lb) 26 fl oz (52 fl oz/a/yr) Common Name and Broadcast Rate/Acre of Active Ingredient glufosinate glyphosate + metolachlor glyphosate + metolachlor + atrazine glyphosate + metolachlor + mesotrione glyphosate ( lb) Remarks USE ONLY ON LIBERTY-LINK CORN HYBRIDS. APPLICATIONS OF LIBERTY 280 TO NON-TOLERANT HYBRIDS WILL RESULT IN SEVERE CROP INJURY AND/OR CROP DEATH!! Can be applied postemergence from the time of crop emergence until the corn has reached the V5 stage. Liberty 280 is a broad-spectrum herbicide with limited systemic activity. Possesses no soil residual activity. Effective on a number of grassy weeds including Texas panicum, but grasses must be between 3 and 6 inches in height for consistent control. Several broadleaf species, particularly morningglories and volunteer peanuts, are easily controlled with Liberty 280. Complete coverage is essential - use with at least 20 gallons water/acre and flat fan nozzles. Adding ammonium sulfate at 17 lb/100 gal will improve herbicide activity. Should be tank-mixed with atrazine for broader spectrum and more consistent control. Do not apply more than 2 applications per season or exceed a total of 44 ozs/a/ season. Applications of Liberty 280 should be made between dawn and 2 hours before sunset for optimum weed control. Rain-free period is 4 hours. Treated corn can be harvested for silage within 60 days after treatment. For Roundup Ready Hybrids Only. Sequence can be used for improved control of tropical spiderwort and Palmer amaranth. Do not exceed 5 pt/a/yr. Can be tank-mixed with atrazine. Can be applied preemergence on any corn hybrid, or postemergence on Roundup Ready Hybrids only. Can be applied over-the-top for corn up to 12 in height. It is recommended that this product be applied postemergence only, to Roundup Ready Hybrids. Can be applied from corn emergence to 30. Should be applied with a non-ionic surfactant and ammonium sulfate. Can be tank-mixed with atrazine for broader weed control spectrum. FOR USE ONLY ON ROUNDUP READY CORN HYBRIDS. APPLICATIONS OF GLYPHOSATE TO NON-TOLERANT HYBRIDS WILL RESULT IN SEVERE CROP INJURY AND/OR CROP DEATH!! Can be tankmixed with atrazine, Dual, Harness, Harness Xtra, Micro-Tech, Bullet, Partner, or Permit herbicides. Various formulations of glyphosate are available. Not all formulations of glyphosate are labeled for use on RR corn hybrids. Please refer to specific product label. Sequence is a premix of glyphosate + S-metolachlor. Expert is a pre-mix of glyphosate + S-metolachlor + atrazine. USE RATE TABLE (lb ae/a): RR-Corn 2 Normal Rate: 0.75 lb Maximum Rate: 1.12 lb Maximum Total In-Crop: 2.25 lb Application Timing: V8 or 30 (up to 48 w/ drop nozzles) RR-Corn Normal Rate: 0.75 lb Maximum Rate: 0.75 lb Maximum Total In-Crop: 1.5 lb Application Timing: emergence to V8 or 30 8

9 Table 4. Estimated Effectiveness of Recommended Herbicides on Common Weeds in Florida Corn 1 Herbicides Sutan+ Atrazine Dual Magnum Time of Application Python Pendimax or Prowl or Prowl H 2 O Glyphosate Atrazine Callisto Accent PPI PRE PRE PRE PRE POT POT POT POT WEEDS BROADLEAF Bristly starbur P G P E P G-E E - P Cocklebur P G-E P G P E E G P FL beggarweed P E F-G F-G P G G - P FL pusley G-E E G-E E G-E F E - P Morningglories F-G G P F-G P F-G G P-F P Pigweed G-E E E E G-E E E G P Ragweed F E F G P G-E E F-G P Sicklepod F-G G P G P G-E E - P Crabgrass E G E P E E P P P Goosegrass E G E P E E P P P Johnsongrass (from seed) GRASS E F F P G-E E P P G-E Sandbur E G G P G-E G P - G-E Texas panicum G-E P P P G-E E F - G-E Annual ryegrass P G -- - G-E Purple nutsedge G P P P P F-G P - P Yellow nutsedge G-E P P P P F-G P - P SEDGE 1 Estimated effectiveness based on rates recommended in this report. Effectiveness may vary depending on factors such as herbicide rate, size of weeds, time of application, soil and weather. Weed Control Symbols: E = % control; G = 80-90% control; F = 60-80% control; P = less than 60% control. Time of Application Symbols: PPI = Preplant Incorporated; PRE = Preemergence; POT = Postemergence Broadcast. 9

10 Table 5. Estimated Effectiveness of Recommended Herbicides on Common Weeds in Florida Corn, continued. 1 Herbicides Basagran 2,4-D Banvel/ Clarity Distinct Sempra Liberty 280 Treflan, Pendimax or Prowl Evik Lorox Gramoxone Time of Application POT POT POT POT POT POT POT PDS POT/PDS PDS WEEDS BROADLEAF Bristly starbur E G G G-E G G-E P E G G-E Cocklebur E E E E G G-E P E G-E E FL beggarweed P G G G P G P E G G-E FL pusley F G G G -- G-E E G G G Morningglories F-G E E E P-F G-E P F-G G G Pigweed G E E E F-G G P G E G-E Ragweed F-G E E E G G P G-E E G-E Sicklepod P E E E P G P G G-E G-E Crabgrass P P P P P G-E E F-G G-E E Goosegrass P P P P P G-E E G G-E E Johnsongrass (from seed) GRASS P P P F-G P E G P-F E G Sandbur P P P - P G G E E G Texas panicum P P P - P G-E E G G E Annual ryegrass P P P - P F-G F F F F-G Purple nutsedge P P P P G F P P G G Yellow nutsedge G P P P G F P P G G SEDGE 1 Estimated effectiveness based on rates recommended in this report. Effectiveness may vary depending on factors such as herbicide rate, size of weeds, time of application, soil and weather. Weed Control Symbols: E = % control; G = 80-90% control; F = 60-80% control; P = less than 60% control. Time of Application Symbols: PPI = Preplant Incorporated; PRE = Preemergence; POT = Postemergence Broadcast. 10